Influencing Factors Analysis of Seismic Responses of Water Immersed Tunnel

In order to study the seismic response of immersed tunnels with different joints and under overlying water, large scaled shaking table tests and immersed tunnels seismic response simulations were carried out. The main material of immersed tunnels model was granular concrete. The model scale ratio designed in the tests was 1∶ 30. Laminated shear boxes filled with sand were used in the tests to form the site. The viscous-spring artificial boundary and equivalent load method were adopted in simulation analysis. The results show that acceleration amplification factors of flexible joint immersed tunnels are smaller than rigid joint immersed tunnels in the same layer. The acceleration amplification factor is less than 1 when the soil layer appears liquefied. Under the earthquake, the maximum values of tunnel section shearing stress peak reduce by 20% and 33%, axial stress peak reduce by 16% and 30% and strain peak increase by 60% and 140% when tunnel joint stiffness(G) reduce to 0.10G and 0.01G. Overlying water site makes acceleration amplification factors smaller, because the overlying water makes the site damping increases.Under the vertical earthquake, overlying water increase from 10 m to 40 m, maximum values of tunnel section shearing stress peak, axial stress peak and strain peak increase by 3%−5%, 30%−40% and 12%−17%, respectively.